Postgres batch write very slow - what to do

[femski <hypertree(at)yahoo(dot)com>]

Folks !

I have a batch application that writes approx. 4 million rows into a narrow
table. I am using JDBC addBatch/ExecuteBatch with auto commit turned off.
Batch size is 100. So far I am seeing Postgres take roughly five times the
time it takes to do this in the Oracle. 

I have played with many parameters. Only one that seems to have any affect
is fsync - but thats only 10% or so. 
Initially I got the warning that checkpoints were happening too often so I
increased the segments to 24. Warnings stopped, but no real improvement in
performance.

Is postgres really that slow ? What am I missing ? 

Here are the changes to my postgressql.cong file. 

shared_buffers = 768MB
work_mem = 256MB 
maintenance_work_mem = 128MB
fsync = off 

checkpoint_segments = 24
autovacuum = on 

Thank you,

-Sanjay
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